Some talk about disease as if it were a poison, whose power can be destroyed by the appropriate agents, very much as an alkali neutralizes an acid. All medicines which do not have this neutralizing influence are, in their view, mere palliatives. It is this idea which lies at the foundation of the opinion, so often expressed, that opium never cures any real disease, but merely gives temporary relief. No opinion can be more erroneous than this. Opium, in its various forms, is one of our chief means of _curing_ disease, as well as of alleviating its sufferings. It is an effectual remedy for many painful affections. For example, it is the great remedy for spasmodic colic. There are auxiliary remedies, which can be used with profit, it is true; but after all opium is the chief remedy. And in the great majority of cases of disease, with which the physician meets in his daily practice, opium materially assists in its cure, by soothing and quieting the irritation of the system, so that the curative power of nature (the vis medicatrix naturæ, of which so much was said in my first chapter), may pursue undisturbed and without hindrance, her processes of restoration. Another error, to which this idea of the neutralizing influence of medicines gives rise, is this. What is found to be useful in any disease is supposed to be so in all cases of that disease. If a remedy be “good” for a certain malady, fever for example, it is apt to be considered as being “good” in all cases of fever, without regard to circumstances. There is a great proneness to suppose all cases of one disease to be alike, and to require therefore similar remedies. The physician finds it difficult often to make people understand that two cases, in which the disease bears the same name, may require very different, and perhaps almost opposite modes of treatment. The accompanying circumstances of disease vary so much in different cases, that this supposed invariable relation of particular remedies to the cure of particular diseases is impossible. This remark applies even to our most efficient remedies. Colchicum is one of the most effectual remedies which we have for rheumatism; and yet there are many cases of this disease, in which its use is forbidden by the condition of the patient.